This invention relates in general to testing communications systems, and more particularly to testing by simulation.
The difficulties of testing military tactical communications systems for vulnerability to electronic warfare jamming are known. To perform realistic jamming tests, actual jamming signals must be radiated. Such jamming signals interfere with other systems operating in, or close to, the jamming testing area. Therefore, jamming tests must be limited in location and to late night or early morning hours. In addition, the frequencies, power levels, and jamming modulation types used may be subject to restrictions imposed by security and safety personnel, by the Federal Aviation Administration and by the Federal Communications Commission. If the jamming signal radiator must be airborne, the cost of conducting the test will be high. Repeatability of test conditions is also a major concern because of the difficulty in duplicating environmental variations.
It is therefore one object of this invention to simultaneously test the jamming vulnerability of a plurality of xe2x80x9cvictimxe2x80x9d communications systems without having to radiate actual jamming signals.
It is another object to carry out such testing while correcting for environmental variations between tests.
It is yet another object to test the jamming vulnerability of the xe2x80x9cvictimxe2x80x9d communication systems to a plurality of jamming signal sources in two operating bands.
These and other objects of the invention are achieved by an apparatus for electronic warfare signal simulation. The simulation apparatus is used together with a remote radiator of a signal free of jamming effects, and a remote radiator of one or more radio frequency control signals which represent one or more predetermined jamming threats in the low and mid bands. The simulation apparatus has a pair of coupling means, each adapted to be connected between a respective one of a plurality of xe2x80x9cvictimxe2x80x9d antennas and its associated xe2x80x9cvictimxe2x80x9d receiver. One coupling means couples off control signals representing jamming threats in the low band from the received signals and passes them to a receiving circuit. The other coupling means couples off control signals representing jamming threats in the mid band from the received signals and passes them to the receiving circuit. The simulation apparatus contains a plurality of modules for generating simulated jamming signals each having a waveform representative of the jamming threat represented by a respective control signal. On command from a control means in the simulation apparatus, the receiving circuit measures the level of the received control signals which is the level an actual jamming signal from the corresponding jamming threat would had. A band select circuit translates the frequency of each simulated jamming signal to the frequency of the jamming threat to which it corresponds, sets its level to the jamming level determined for its control signal, replicates the xe2x80x9cvictimxe2x80x9d antenna gains, and feeds the modified simulated jamming signals together with the desired signal to the plurality of xe2x80x9cvictimxe2x80x9d receivers. In this way, the simulation apparatus replicates the jamming signals that would have been received by the xe2x80x9cvictimxe2x80x9d receivers had they come from actual jamming sources.
The simulation apparatus is preferably of modular construction. The modular nature of the system enhances the performance in two ways. First, the system is easily maintained and upgraded because the modules can be removed and replaced without impact to the mechanical design or software control. Second, because each of the radio frequency modules in the system is housed in a separate radio frequency isolated compartment, cross-talk and interference between the various stages of the radio frequency chain are prevented thereby increasing the spectral purity of the simulated jamming signals.
Additional advantages and features will become more apparent as the subject invention becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: